1. Field of the Invention
The present invention relates to an information processing apparatus including a plurality of hard disks, a control method of the information processing apparatus, and a recording medium.
2. Description of the Related Art
As a measure for a failure of hard disks, a mirroring technique is known, which records identical data in a plurality of local hard disks. When mirroring is implemented, even if a failure occurs in a hard disk, an ongoing processing can be continued by using another hard disk, which improves reliability.
A mirroring system, which performs mirroring, is provided with a function to rebuild (build again) data. Rebuild is a function to recover data of a failed hard disk (HDD) from a remaining trouble-free HDD when a failure occurs in one of two HDDs. For example, rebuild is performed to achieve consistency between the operating HDD and a HDD mounted to replace the failed HDD.
The mirroring system further includes a so-called patrol function configured to correct errors by reading all sectors of the two HDDs and rewriting the sectors of the error-detected HDD by data from the other HDD.
In the mirroring system provided with the functions described above, generally, while power to a host computer is discontinued or the host computer enters a sleep mode, power supply to the mirroring system is stopped and goes into a power-off state. When the power supply to the mirroring system turns off while the mirroring system is executing rebuild processing, information as to how far a rebuild processing has been executed is recorded in a non-volatile memory in the mirroring system.
When the host computer is restarted or returns from the sleep mode, the mirroring system automatically resumes the rebuild processing, which has been interrupted, according to information stored in the non-volatile memory.
Rebuild (or patrol) processing is usually executed for each predetermined number of blocks. When a HDD read/write request is sent from the host computer connected to the mirroring system during a rebuild processing, HDD read/write operations requested by the host computer are executed in time slots between blocks of rebuild processing.
Therefore, if the blocks of the rebuild processing are divided in large size units, there is a problem that the response to requests from the host computer will be slower.
To solve this problem, Japanese Patent Application Laid-Open No. 2007-94994 discusses a technique in which when HDD access requests frequently come from a host computer, by recasting the blocks of rebuild processing into smaller units, the response to HDD access requests from the host computer can be made quicker.
By using the technique described above, the response to HDD access requests from the host computer can be accelerated. However, even if the blocks of the rebuild processing are reduced into smaller units, the response speed remains unimproved compared to a case where the rebuild processing is not performed.
The HDD is accessed frequently particularly when the host computer is started, because a boot program of the entire system is stored in the HDD. If the interrupted rebuild processing is resumed automatically, a problem arises that the start-up time of the system is prolonged.